This thesis investigates whether the overall toughness of the material can be improved by promoting multiple delaminations. This is done by first investigating state-of-the-art methods regarding materials that exhibit toughening behaviour during fracture initiation. This behaviour can be achieved by introducing weakening patches between the material interfaces. In order to validate the results found in the literature, experimental testing of a glass fiber reinforced polymer (GFRP) double cantilever beam (DCB) containing a weakening patch configuration was conducted. These DCB specimens were tested under quasi-static and fatigue loading conditions. The results showed that under quasi-static loading, no toughening was observed in the DCB beams tested. In the context of fatigue testing, the characterization of this test revealed toughening behaviour in the test specimens. These studies proposed a novel contribution to state-of-the-art methods by providing a new benchmark case for the study and prediction of multiple fatigue-driven delaminations in GFRP specimens.